You don't submit a robots.txt file to Google Webmaster. A robots.txt file goes on your website and informs search engines of content you don't want them to index. Google Webmaster has a robots.txt file analyzer, but it is just looking at the file already on your website.

Thanks for your response but think we or i got my wires crossed. Basicly when your in google webmaster there is an area which checks whether it can access your robot.txt file and at the time is wasn't saying it was a success. I had already set up a site map using that plugin you suggested and submitted it and it was fine, but when i tried to access the XML sitemap withing the yoast plugin, it was coming up as

<---- Not Found

The requested URL /sitemap_index.xml was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.----->

The robot.txt file has been found now though so prob just needed to wait and i have set-up a XML site-map using you plugin... so thank you for taking the time to help me out! Very much appreciated :-))